Minor core header cleanups

core/include/common_macros.h

@@ -13,7 +13,7 @@
 #define UNUSED __attributed((unused))
 
 #ifndef BIT
-#define BIT(X) (1<<X)
+#define BIT(X) (1<<(X))
 #endif
 
 /* Use this macro to store constant values in IROM flash instead

core/include/esp/gpio.h

@@ -7,6 +7,7 @@
  * BSD Licensed as described in the file LICENSE
  */
 #ifndef _ESP_GPIO_H
+#define _ESP_GPIO_H
 #include <stdbool.h>
 #include "esp/registers.h"
 #include "esp/iomux.h"